| 摘要 |
PURPOSE:To prevent any defective welding which might be caused due to electric discharge developing within an electron gun by detecting change in the acceleration voltage of a beam irradiated on a substance to be worked, and stopping the operation of the electron gun during selected arbitrary time only when the acceleration voltage becomes smaller than the set point by over 10%. CONSTITUTION:A high voltage power source 1, an electron gun 2 and a vacuum tube 13 constitute a high-voltage main circuit. The electron gun 2 is used to perform welding of a substance 6 to be worked by accelerating an electron beam 5 by applying high voltage to thermions discharged through heating carried out with a cathodic power source 3 after they are controlled with a bias power source 4. When abnormal electric discharge develops within he electron gun 2, the output of an acceleration-voltage detector 7 changes, and the output is compared with that of a voltage setting device 8 by means of a comparing circuit 9. Only when the acceleration voltage becomes smaller than the set point by over 10%, a multivibrator 10 and a control transistor 11 work cutting off the high voltage circuit. Time during which the operation of the electron gun 2 is stopped is regulated to below 10msec, and turning on or turning off time is regulated to 500musec to 1msec. By the means mentioned above, any defective welding which might be caused due to electric discharge developing within the electron gun 2 can be prevented. |
